Yezzi M J, Blakely E A, Tobias C A
Division of Biology and Medicine, Lawrence Berkeley Laboratory, University of California, Berkeley 94720.
Radiat Res. 1988 May;114(2):281-96.
A temperature-sensitive mutant for protein synthesis, CHO-tsH1, has been compared to the wild-type (WT) cell, CHO-SC1, in single- and split-radiation-dose schemes. When the exponentially growing mutant and the wild-type cells were treated at 40 degrees C for up to 3 h prior to split doses of X rays, survival was progressively reduced in the mutant compared to the wild type. In addition, if a 2-h split-dose scheme was used with a treatment of 40 degrees C given before the first dose, between the dose fractions and after the second dose, the recovery from sublethal damage (SLD) was almost completely inhibited in the mutant cells. These observations implied that a pool of proteins was involved in the recovery from sublethal X-ray damage. However, if molecular repair was measured in the mutant cell by the alkaline-unwinding technique under the same time and temperature schemes as those demonstrating a reduction in the recovery from SLD, no difference in the kinetics of DNA strand rejoining was observed compared to similar measurements made under conditions permitting SLD recovery. Misrepair processes may permit restoration of DNA strand integrity but not allow functional repair. Split-dose experiments were also done using cycloheximide to chemically inhibit protein synthesis. Under conditions which mimicked those used in the temperature-shift experiments both cell lines showed a reduction in the recovery from sublethal damage comparable in magnitude to that observed in the mutant cells when they were treated with 40 degrees C. Both the chemical and thermal inhibition of protein synthesis substantiate its necessity for the recovery from sublethal damage.
已将一种蛋白质合成温度敏感突变体CHO-tsH1与野生型（WT）细胞CHO-SC1，在单次和分次辐射剂量方案中进行了比较。当指数生长的突变体和野生型细胞在分次X射线照射前于40℃处理长达3小时时，与野生型相比，突变体的存活率逐渐降低。此外，如果采用2小时分次剂量方案，并在第一次照射前、两次照射之间以及第二次照射后给予40℃处理，突变体细胞中从亚致死损伤（SLD）的恢复几乎完全受到抑制。这些观察结果表明，一组蛋白质参与了从亚致死X射线损伤中的恢复。然而，如果在与显示SLD恢复减少相同的时间和温度方案下，通过碱性解旋技术在突变细胞中测量分子修复，与在允许SLD恢复的条件下进行的类似测量相比，未观察到DNA链重新连接动力学的差异。错配修复过程可能允许恢复DNA链完整性，但不允许功能修复。还使用环己酰亚胺进行了分次剂量实验，以化学方式抑制蛋白质合成。在模拟温度转换实验所用条件的情况下，两种细胞系从亚致死损伤中的恢复均有降低，其幅度与突变细胞在40℃处理时观察到的相当。蛋白质合成的化学抑制和热抑制均证实了其对于从亚致死损伤中恢复的必要性。
